The starting dose of GDC-6036 in the combination Arms B, C, D, E, F and G will be determined from Stage I Arm A (single-agent dose escalation).
A 1200 milligram (mg) intravenous (IV) infusion of atezolizumab will be administered on Day 1 of 21 day cycles.
Cetuximab will be administered at an initial dose of 400 milligram per square meter (mg/m^2) IV infusion followed by 250 mg/m^2 IV infusion weekly in 21 day cycles.
A 15 milligram per kilogram (mg/kg) IV infusion of bevacizumab will be administered on Day 1 of 21 day cycles.
150 mg of erlotinib will be administered PO QD in 21 day cycles.
The starting dose of GDC-1971 will be determined from its single-agent dose escalation.
The starting dose of inavolisib will be determined from its single-agent dose escalation.